Is Your Airplane Ready For DRVSM?


On its face, RVSM sounds simple enough — compress the distance between aircraft operating in the high-altitude en route environment. But its not that simple, or easy. For one thing, there are very good reasons previous standards at those altitudes called for 2000 feet of separation. Among them are the unreliability of altimetry and autopilot systems installed in older airplanes. Additional challenges are related to limitations of existing ATC equipment, Mode C altitude-reporting resolution and how quickly a seemingly minor altitude deviation can quickly become a major loss of separation with closure rates of 1100 knots or more. As such, RVSM airspace throughout the world and, beginning in January here in the U.S., will be considered special qualification airspace, according to the FAA. Both the individual operator and the specific aircraft type or types in use must be FAA-approved before the operator conducts flight in RVSM airspace. The biggest challenge is gaining RVSM approval from the FAA for older airframes. While the equipment necessary to bring, say, an older Hawker or Lear into RVSM compliance differs from airframe to airframe — along with the costs — the FAA says minimum equipment should include two independent altimetry systems, an SSR altitude reporting transponder, an automatic altitude control system, an altitude alert system and a TCAS II installation running software version 7.0 or later. The margins for error in these systems get tighter, too. For example, the altitude alert threshold is +/- 300 feet for aircraft types certificated before 1997; its +/- 200 feet for aircraft certificated after that date. And then all this hardware and software has to be monitored and tested on an ongoing basis, sometimes by literally flying the aircraft over a ground-based monitoring station. Look on the bright side: You probably wont have to go through TSA screening.